Assessment of Microneedles for Transdermal Drug Delivery

Microneedle (MN) arrays are a minimally invasive method of bypassing the stratum corneum barrier via piercing of the epidermis, creating reversible microscopic channels into the microcirculation. The concept of microneedle technology has developed significantly since its conception in 1976, and throughout this time has been used to enhance topical and transdermal drug delivery, deliver vaccines, detect endogenous markers for patient monitoring and diagnosis, and improve the appearance of skin through cosmeceutical delivery. Currently, five types of MNs exist, which can be fabricated from numerous materials to control and extend drug release where necessary. This chapter first defines MNs and discusses their fabrication techniques and materials. Second, the numerous applications of MNs are discussed, from enhancement of drug and vaccine delivery to improvement of skin appearance. The true potential of MNs as a drug delivery device for biopharmaceuticals will not only rely on acceptance from prescribers, patients, and the regulatory authorities but the ability to upscale MN manufacture in a cost-effective manner and the long-term safety of MN application. Thus, the current barriers to clinical translation of MNs and how these barriers may be overcome are also discussed.